Check valves may be used, for example, to prevent back flow through a conduit. When flow in the desired direction occurs through the conduit, the check valve will automatically be opened by the pressure of the flow. Where such flow is provided by a pump, such a check valve will normally always be open during proper operation of the pump.
In some applications, therefore, check valves having check valve arms or handles are used. Such check valve arms are disposed outside the conduit but are mechanically connected to the associated valve, whereby the position of the valve inside the conduit can be manually controlled when desired by manipulating the handle. Further, the position of the valve can be visually determined based on the position of the check valve arm.
Of course, visual inspection of valves is not adequate in many situations, as they may not be in conveniently seen locations, and will typically operate round the clock whereby constant operator supervision would be impractical and/or impossible. Therefore, limit switches have heretofore been used to detect pump failure by detecting whether or not a check valve is closed when the pump is supposed to be operating. However, limit switches are expensive, and are difficult to install and adjust.
Mercury switches have also been used to detect pump failure based on detection of a closed check valve when the pump is supposed to be operating. However, such switches have required clear tube switches in order to be able to see whether the switch is making contact in the proper valve position. This requires that the tubes be exposed so that they can be seen, which also makes them particularly susceptible to breakage. Further, even where the switch appears to an observer to be making contact, it can be difficult to determine visually whether or not such contact is steady. To overcome this, or where the switch has not been adequately visible, cumbersome additional equipment, such as meters or test lights, have been used to ensure proper positioning of the switch relative to the check valve arm.
The present invention is directed toward overcoming one or more of the problems set forth above.